An effective thermal management system is vital for improving the range and safety of electric vehicle.This study addressed the thermal management needs of a particular vehicle model by developing a centralized water-based thermal manage-ment module with a ten-port valve as its core component.Using the K-e model in STAR CCM+,a CFD simulation of the in-ternal flow field was performed,followed by structural optimizations based on the simulation results.After optimization,pressure losses in all circuits are significantly reduced,and flow turbulence is markedly improved.The results show that the maximum simulation error is within 5.79％,and the system's maximum back pressure do not exceed the pump's rated pressure.This proved that the designed module meets the vehicles thermal management performance requirements,resulting in notable enhancements to the vehicle's thermal performance and energy efficiency.
A double L-shaped heat pipe sink that uses a micro heat pipe array is proposed for heat dissipation and temperature uniformity in high-power electronics chip cooling for the first time in this work. The radiator is composed of two L-shaped micro heat pipe arrays filled with copper foam wick (the composite wick structure) and aluminum flat fins, which can reduce the temperature of hotspots of electronics effectively and has good inclination adaptability. Through experiments, the heat transfer performance is studied under different copper foam filling lengths, liquid filling rates, and inclination angles. Then, a numerical simulation of the effect of different fin parameters on the radiator is conducted using Icepak. The composite wick structure effectively enhances the heat transfer capability of the radiator. Results show that the average thermal resistance of the micro heat pipe array with a composite wick structure is 0.258 K/W, indicating a 23 % reduction compared with that of a single wick structure double L shape heat pipe sink. The double L shape heat pipe sink solves the phenomenon of chip temperature jump caused by the hotspots of high heat flux. The average temperature of the chip surface can be controlled below 62 degrees C when the localized heat flux is 200 W/cm2. Simulation results show that optimization of the fin structure can stabilize the temperature of the 214 W chip at 70.1 degrees C, which is reduced by 8.7 % than before optimization.
The Tianhuan One is the first magnetically-confined plasma device in China using a magnetically floating dipole field magnet.According to the overall objectives and design requirements of the CAT-1(China Astro Torus-1)device,a sim-plified linear current model was used to analyze and calculate the stability of the floating magnet based on methods such as vector magnetic field,mechanical balance and dynamics.The design parameters of the floating magnet,levitation coil,and Tilt-Slider-Rotation coil in the device were given,including the overall size,spatial position and layout,current,weight,characteristic stability performance and their relationship.The results show that the optimal value of the levitation coil radius is 1.7 m and the corresponding current is 3.49 kA for the design goals of the floating magnet with the weight of 1 200 kg,current of 5 MA and sus-pension height of 2.0 m.In order to achieve effective resistance and control of the floating magnet offset movement,the working area near the balance point should be limited to|Δz|＜100 mm,|Δer|＜50 mm and|Δα|＜π/24.
The cryogenic system of the 6T superconducting Wiggler magnets at the Hefei National Synchrotron Radiation Laboratory was upgraded. During the upgrade process, the original copper leads of the superconducting Wiggler magnets are replaced with two 460A high-temperature superconducting current leads and three 20A high-temperature superconducting current leads, reducing the heat load of the cryogenic system. Five HTS current leads can be cooled using a GM cryocooler based on the optimal design and experimental verification of their current-carrying capability and heat load. According to the loading current experimental data, the running voltage and operating temperature are stable. The results of the overcurrent capacity experiments demonstrate that the maximum loading current of the 20A high-temperature superconducting current lead can reach 142A and that of the 460A high-temperature superconducting current lead can reach 780A.
中国科学院等离子体物理研究所(ASIPP)开展了一项研究活动,来评估CFETR环面真空室低温泵中冷屏挡板的热屏蔽性能.采用数值模拟方法,通过设计对照组的方式对不同排布方式下冷屏挡板的热屏蔽性能进行了对比性分析.结果表明:相比于无冷屏挡板结构,布满45度倾斜角的冷屏挡板能够将吸附板表面的辐射热负载降低53.8％;相比于背向阀头的冷屏挡板结构,采用面向阀头的冷屏挡板结构能够将吸附板表面的辐射热负载降低37.5％;当坐标超过0.45 m,冷屏挡板的最大设计间距为30 mm,当坐标超过0.6 m,冷屏挡板的最大设计间距为60 mm,当坐标超过0.94 m,冷屏挡板的最大设计间距为90 mm.
对第二代高温超导带材堆叠的准各向同性高温超导股线进行仿真,研究其在不同温区下的交流损耗.首先采用自洽模型获得20 K至77.5 K下超导股线的自场临界电流和磁场分布,然后通过T-A算法计算超导股线在不同温区下的传输不同幅值、频率的传输交流损耗.仿真结果表明,准各向同性高温超导股线在不同温区下的传输交流损耗与传输电流大小成正比,且温度越低传输交流损耗越大;不同温区下超导股线的传输损耗与频率无关.这对准各向同性超导股线应用于高场强磁体的冷却系统效率及热负荷的预估具有重要的参考意义.
通过研究可调谐滤波器的基本原理,提出了一种奇、偶模频率分别可控的双模谐振器,采用砷化镓变容二极管作为调谐元器件,实现了高温超导带通滤波器的连续可调谐.基于全波电磁仿真分析方法,在YBCO/MgO基片上成功设计、制作了四节高温超导可调滤波器.测试结果表明,该滤波器的可调频率范围为1.296～1.526 GHz(16.3％),验证了该设计方法的有效性.
无绝缘高温超导线圈因其良好的电热稳定性和自保护特性得到广泛应用,但其在高场超导磁体的应用过程中存在失超保护安全边界性问题.针对无绝缘高温超导线圈,利用高温超导线圈等效电路网格模型,建立了无绝缘高温超导线圈失超传播的电、磁、热多物理场耦合模型,基于MATLAB商业软件采用数值模拟方法得到了不同导热环境下及不同外加磁场强度下无绝缘高温超导线圈失超过程中的电压、温度、磁场的分布规律.研究结果表明,局部失超发生时,绝热环境下的线圈失超传播范围广且恢复时间长,线圈呈现先匝内后匝间的失超传播规律,失超电压和磁场与失超匝数直接相关.
为解决电动汽车制冷剂直接冷却电池热管理系统(简称直冷系统)因出口段制冷剂处于过热状态而造成的电池温度分布不均,在直冷板后增加二次节流装置改善制冷剂在系统内的两相分布,从而提升系统温控能力.利用AMESim仿真平台建立双节流系统模型,设计开度固定和开度可调节两种二次节流方案并分析温控性能.结果表明,采用双节流结构可以提升直冷板内蒸发温度,消除出口过热现象,在充电工况下相比原直冷系统电池最高温度降低9.03％,在不同充电倍率和NEDC行驶工况下均能保持电池单元最大温差小于5℃.开度固定方案仅在设计工况范围内具有较好温控效果,而开度可调节方案能够自动调节开度,在不同工况下均能保持直冷板出口处制冷剂为两相状态而压缩机入口为过热状态,提升系统均温能力.
针对急冻设备工作过程中蒸发器表面结霜问题,设计了一种基于冷凝器余热回收的蓄热-气动式除霜系统.采用CFD仿真与实验相结合的方法设计蓄热器,搭建除霜传动机构实现喷气管上下运动.研究结果表明,正六边型蓄热体蓄热效果好、压降低.蓄热器加热到44℃时与冷空气进行热交换,蓄热器出口处空气温度在5.5 min内能够保持在25℃以上.蒸发器表面开始融霜时,传动机构停留5 s后以100 mm/min的速度运行130 s,蒸发 器表面融霜区域达660×100 mm.研究结果为急冻间内蒸发器除霜提供可靠的理论依据.
基于H方程求解了110 kV/3 kA高温超导电缆在不同工况下运行时的磁场分布和交流损耗,在此基础上分析屏蔽层感应电流的变化情况,并探究导电层和屏蔽层采用组合超导带材的可行性.结果表明,随着传输电流的增大,屏蔽层感应电流发生了畸变,电缆总体的交流损耗显著增加.当导电层采用77 K下临界电流为210 A的超导带材时,电缆可显著降低大约48％的交流损耗.
针对河南移动通信基站机柜空调温控效果较差、能耗较高、柜内设备常发生高温报警等突出问题,提出采用热管与空调复合技术方案,开发了一体化产品样机,并对郑州地区基站机柜空调进行试点改造应用,实测结果表明:相对原机柜空调,热管与空调复合技术保证全年基站机柜温度在10℃～39℃之间,符合国家标准,柜内BBU(Building Base band Unit)设备无高温报警,基站全年 PUE(Power Usage Effectiveness)由原来的 1.7 降为 1.2,降低了 29％,节能效果十分显著.
本文详细介绍了G-M型制冷机低温泵冷屏和障板的热力学仿真、低温泵减振设计和抽氢性能研究.G-M型制冷机低温泵开机降温,完成减振低温泵振幅测试和抽氢性能试验.减振低温泵的泵口振幅降至±0.096 μm,低温泵实际抽氢速率优于14 000 L/s,与设计相符,满足客户使用需求.
基于单相泵驱流体回路,研究了系统在不同拓扑结构下的控温性能.采用集总参数法建立了流量计算及分配模型、流体与设备换热模型、混合点温度计算模型以及热流计算模型,并运用Openmodelica仿真平台,开展了不同拓扑结构对设备温度、系统流量和系统出口工质温度的影响分析,探究了不同载荷占空下设备散热效果、系统峰值损耗和内能变化等的动态特性.结果表明,一方面,并联拓扑体系设备散热及均温效果较好;另一方面,热惯性对系统内能变化影响较大,在系统热惯性一定的条件下,载荷占空比越大工质冷却响应时间越大,系统能量损失越小.
掌握充电模块最高温度和充电时间是避免充电桩发生火灾的关键.为了探究相变材料(PCM)用量对充电模块最高温度和充电时间的影响,基于热比理论,实验分析了不同产热功率和风速条件下充电模块最高温度和充电时间变化.结果表明:增大热比可以降低充电模块的最高温度,产热功率25 W时效果最好,最高温度降低3.7℃.在较高风速条件下,热比作用对充电模块最高温度影响变化明显,热比等于0.4为实现充电模块热管理性能最佳指标值.增加热比可以提升充电时间,热比为0.5时充电时间最长.产热功率为25 W时,增加热比充电时间最多延长了 330 s.
针对车载相控阵测控系统T/R组件集成度高、热流密度大等散热难题,设计了一种高可靠性的液冷环控系统,包括液冷机组和管网系统两部分.通过对泵、压缩机以及系统控制流程的设计优化,结合末端环形管网的流量分配设计,该液冷环控系统制冷量、供液流量等均优于技术指标要求,末端流量分配精度≤4％,解决了车载相控阵测控系统的散热问题.
针对急冻间内冻品摆放方式对内部流场和温度场的影响,采用CFD模拟与实验相结合的方法,在空载工况下将数值模拟结果与实验测量的速度分布数据进行对比,验证标准k-e模型的合理性.采用标准k-ε模型,通过数值计算获得不同货架位置、冻品层间距离对冻结均匀性的影响.研究结果表明,货架距离过大或过小都将导致温度不均匀性较高,最优货架距离为100 mm,达到完全冷冻需要6.9 h.优化冻品层间距离后达到完全冷冻需要6.8 h,比优化前减少了 6.8％.
用分子动力学模拟方法研究了超临界CO2-POE体系的降压成核过程.当降压过程目标压力靠近临界压力时空化核无法稳定存在.此时密度时间序列曲线波动很大,△g最大可以达到0.18 g/cm3,动能振幅达350 kcal/mol.当系统夹带质量分数15％的POE润滑油时,空化核也无法稳定存在.且径向分布函数的波峰移至4.2 ?,这意味着系统中T形二聚体的比例增加.模拟结果显示:系统含质量分数较高的POE润滑油或降压过程的目标压力接近临界压力时都会变得不稳定,导致成核过程无法稳定进行.
为探究磁场强度和肋片高度对微通道内Fe3O4-H2O纳米磁流体流动换热性能的影响,采用数值模拟的方法,以开放式间断微通道热沉为研究对象,在雷诺数为200到500之间展开数值模拟研究,模拟微通道内流体工质流动换热过程.结果表明:进出口压降随雷诺数的增大而增大,且随着磁场强度的增大,压降的增大趋势愈显著;微通道的换热性能随着磁场强度的增大,呈现出先增大后减小的趋势;通过增加肋片高度,可以有效的提高热沉的传热性能.研究发现,开放型微通道综合换热性能优于封闭型,在所研究的参数范围内,微通道肋片高度达到0.9 mm时,综合换热性能和均温性最佳.
为了提高高温超导脉冲变压器的储能容量,发挥带材的最优性能,以YBCO同轴饼式超导变压器的线圈结构为优化对象,基于最小二乘法对超导带材的临界电流曲线进行拟合,分析了在带材用量相同的情况下,高温超导线圈不同堆叠层数对其临界电流、储能容量及变压器耦合系数的影响.结果表明,在30 K温度下,当原边线圈堆叠层数为5时,可以在较高耦合系数下获得最大储能25.4 kJ,通过增加超导线圈堆叠层数可以提高高温超导脉冲变压器的性能.
